Field of the Invention
The present invention relates to systems, assemblies and processes for controlling equipment, tools and the like that are positioned in a subterranean well bore, and more particularly, to systems, assemblies and processes for controlling a plurality of equipment, tools and the like that are positioned in a subterranean well bore.
Description of Related Art
In the production of fluid from subterranean environs, a well bore is drilled so as to penetrate one or more subterranean zone(s), horizon(s) and/or formation(s). The well is typically completed by positioning casing which can be made up of tubular joints into the well bore and securing the casing therein by any suitable means, such as cement positioned between the casing and the walls of the well bore. Thereafter, the well is usually completed by conveying a perforating gun or other means of penetrating casing adjacent the zone(s), horizon(s) and/or formation(s) of interest and detonating explosive charges so as to perforate both the casing and the zone(s), horizon(s) and/or formation(s). In this manner, fluid communication is established between the zone(s), horizon(s) and/or formation(s) and the interior of the casing to permit the flow of fluid from the zone(s), horizon(s) and/or formation(s) into the well. Alternatively, the well can be completed as an “open hole”, meaning that casing is installed in the well bore but terminates above the subterranean environs of interest. The well is subsequently equipped with production tubing and convention associated equipment so as to produce fluid from the zone(s), horizon(s) and/or formation(s) of interest to the surface. The casing and/or tubing can also be used to inject fluid into the well to assist in production of fluid therefrom or into the zone(s), horizon(s) and/or formation(s) to assist in extracting fluid therefrom.
Often during the drilling and completion of a well or during production or injection of fluid from or into a well or subterranean environs, it can be desirable to control the operation of multiple tools, equipment, or the like, for example perforating guns, cutters, packers, valves, sleeves, etc., that can be positioned in a well. In the production of fluid from or injection of fluid into subterranean environs, multiple tools and equipment are often positioned and operated in a well bore. For example, a plurality of perforating guns can be deployed within a well bore to provide fluid communication between multiple zones, horizons and/or formations. Upon detonation, these guns file projectiles through casing cemented within the well bore to form perforations and establish fluid communication between the formation and the well bore. Often these perforating guns are detonated in sequence. A plurality of flapper valves can be used in conjunction with multiple perforating guns to isolate the zone, horizon or formation being completed from other zones, horizons and/or formations encountered by the well bore. As another example, packers can be deployed on a tubular and expanded into contact with casing to provide a fluid tight seal in the annulus defined between the tubular and the casing. Flow chokes can be used to produce the well from multiple zones with these chokes set at different openings to balance the pressure existing between multiple subterranean zones, horizons and/or formations so that a plurality of such zones, horizons and/or formations can be produced simultaneously.
Hydraulic systems have been used to control the operation of tools positioned in a well. Such systems have a control system and a down hole valve. The control system includes surface equipment, such as a hydraulic tank, pump, filtration, valves and instrumentation, control lines, clamps for the control lines, and one or more hydraulic controller units. The control lines run from the surface equipment to and through the wellhead and tubing hanger to desired equipment and tools in the well. These control lines are clamped usually along a tubular that is positioned within a well. The control lines can be connected to one or more hydraulic control units within a well for distributing hydraulic fluid to the down hole valves.
Several basic arrangements of hydraulic control lines are used in a well. In a direct hydraulic arrangement, each tool that is to be controlled will have two dedicated hydraulic lines. The “open” line extends from the surface equipment to the tool and is used for transporting hydraulic fluid to the downhole control valve to operate the tool, while the “close” line extends from the tool to the surface equipment and provides a path for returning hydraulic fluid to the surface of the earth. The practical limit to the number of tools that can be controlled using the direct hydraulic arrangement is three, i.e. six separate hydraulic lines, due to the physical restraints in positioning hydraulic lines in a well. The tubing hanger through which the hydraulic lines run also has to accommodate lines for a gauge system, at least one safety valve and often a chemical injection line, which limits the number of hydraulic lines the hanger can accommodate. When it is desirable to control more than three tools in a well, a common close arrangement can be employed in which an open line is run to each tool to be controlled and a common close line is connected to each tool to return hydraulic fluid to the surface. Again, the common close system has a practical limit of controlling five tools, i.e. six separate hydraulic lines.
In another arrangement, a single hydraulic line is dedicated to each tool and is connected to each tool via a separate, dedicated controller for each tool. To open the tool, the hydraulic fluid in the dedicated line is pressurized to a first level. Thereafter, the hydraulic fluid in the dedicated line is pressurized to a higher level so as to close the tool. In a digital hydraulics system, two hydraulic lines are run from the surface equipment to a downhole controller that is connected to each of the tools to be controlled. Each controller is programmed to operate upon receiving a distinct sequence of pressure pulses received through these two hydraulic lines. Each tool has another hydraulic line is connected thereto as a common return for hydraulic fluid to the surface. The controllers employed in the single line and the digital hydraulics arrangements are complex devices incorporating numerous elastomeric seals and springs which are subject to failure. In addition, these controllers use small, inline filters to remove particles from the hydraulic fluid that might otherwise contaminate the controllers. These filters are prone to clogging and collapsing. Further, the complex nature of the pressure sequences requires a computer operated pump and valve manifold which is expensive.
In accordance with the “distribution hub” arrangement, two hydraulic lines are run from the surface to one downhole controller to which each tool to be controlled is connected by its own set of two hydraulic lines. This controller can be ratcheted to any of a number of predetermined locations, each of which connects the control lines of a given tool to the control lines running from the surface to the controller. In this manner, each tool can be operated independently from the surface. By ratcheting the controller to another location, another tool can be operated. This arrangement is expensive due to the large number of components and complex arrangement of seals in the controller and unreliable as it is difficult to get feedback to the surface on the exact position of the controller, especially if the operator has lost track of the pulses previously applied. Thus, a need exists for hydraulic control systems, assemblies and processes for use in controlling multiple tools in a well which is relatively inexpensive, simple in construction and operation and reliable.
Further, it is often desirable to stimulate the subterranean environs of interest to enhance production of fluids, such as hydrocarbons, therefrom by pumping fluid under pressure into the well and the surrounding subterranean environs of interest to induce hydraulic fracturing thereof. Thereafter, fluid can be produced from the subterranean environs of interest, into the well bore and through the production tubing and/or casing string to the surface of the earth. Where it is desired to stimulate or fracture the subterranean environs of interest at multiple, spaced apart locations along a well bore penetrating the environs, fluid is pumped into a particular location adjacent the subterranean environs of interest that is farthest from the surface of earth while a means, such as a flapper valve(s), is employed to isolate the remaining locations. Once fluid is pumped under pressure from the surface into the well and the lowermost location, means are actuated to isolate the next location which is closest to the surface from the lowermost location and the remaining locations. Fluid is pumped under pressure from the surface into the well and the subterranean environs adjacent the isolated location so as to hydraulically fracture the same. In this manner, all of the subterranean environs adjacent to the multiple, spaced apart locations can be hydraulically fractured in sequence beginning at the location that is farthest from the surface along the well bore. Conventional systems and associated methodology that are used to stimulate subterranean environs in this manner include casing conveyed perforating systems, ball drop systems, and perforate and plug systems.
However, problems exist with hydraulically fracturing subterranean environs from multiple, spaced apart locations in sequence beginning with location that is farthest from the surface along the well bore. Hydraulic fracturing of subterranean environs creates stress forces in rock that essentially harden the particular regions of the subterranean formation fractured thereby inhibiting propagation of fractures created during hydraulic fracturing of an adjacent region into the region previously fractured. This can cause hydraulic fractures formed in the adjacent region to propagate away from the previously fractured region which may not be desirable. Accordingly, a need exists for a process for sequentially fracturing subterranean environs from spaced apart locations along the well bore in any desired sequence. A further need exists for a process for sequentially fracturing subterranean environs from spaced apart locations along the well bore in a sequence calculated to advantageously use rock stress generated in the subterranean environs to propagate fractures in a desired manner.